General Chemistry 1

1. Lewis
Diagrams

2. How many valence electron does chlorine have?
1
2 3 4 5 6 7
8
Except Helium
It only has 2
valence electrons

3. How many valence electron does chlorine have?
1
2 3 4 5 6 7
8
7 valence electron

4. • Knowing the number of valence electrons an
element has is critical.
• In Lewis Diagram, dots represent valence
electrons
C
Chlorine has 7
valence electron
The dots should be neatly drawn on the 4 sides of the square with no more than
dots on any side.

5. Let’s practice!
1
2 3 4 5 6 7
8
H C O

6. • Lewis Diagram is often used to
represent covalent bonding in
molecules and ions.
• In covalent bonding, atoms share
valence electrons in order to get
a full octet (or duet for H).

7. • Lewis Diagram for H2:
• The shared electrons are counted as
owned by both atoms
This means
that both
hydrogens are
happy because
the both
satisfied the
octet rule

8. H H H H
These are equivalent.
• 1 line = single bond = 2 electrons
• 2 lines = double bond = 4 electrons
• 3 lines = triple bond = 6 electrons

9. • Lewis Diagram for O2:
O O
Oxygen
has 6
valence
electrons
• Also equivalent to
O O
2 lines
=
double bond
=
4 electrons
2 dots are
called a lone
pair of
electrons

10. • Lewis Diagram for N2:
N N
Nitrogen
has 5
valence
electrons
• Also equivalent to
N N
3 lines
=
triple bond
=
6 electrons

11. 5 steps in drawing a Lewis
Diagram
1. Count all the valence electrons on the
molecules.
2. Determine the central atom (the element
there is only of)
3. Draw a single bonds to the central atom
4. Put all remaining valence electrons on atoms
as lone pairs
5. Turn lone pairs into double or triple bonds tp
give every atom an octet (or duet).

12. Example 1: Lewis Diagram of H2O
1. Count all the valence electrons on the
molecules.
H2 = 1 x 2 = 2
# of
electron
# of hydrogen in
the molecule
O = 6 x 1 = 6
Total = 8 v.e.

13. Example 1: Lewis Diagram of H2O
2. Determine the central atom (the element
there is only of)
O
H H

14. Example 1: Lewis Diagram of H2O
3. Draw a single bonds to the central atom
O
H H

15. Example 1: Lewis Diagram of H2O
4. Put all remaining valence electrons on atoms as lone
pairs
5. Turn lone pairs into double or triple bonds tp give every
atom an octet (or duet).
O
H H

16. Example 2: Lewis Diagram of SO3
1. Count all the valence electrons on the
molecules.
S = 6 x 1 = 6
O = 6 x 3 = 18
Total = 24 v.e.

17. Example 2: Lewis Diagram of SO3
2. Determine the central atom (the element
there is only of)
S
O O
O

18. Example 2: Lewis Diagram of SO3
3. Draw a single bonds to the central atom
S
O O
O

19. Example 2: Lewis Diagram of SO3
4. Put all remaining valence electrons on atoms
as lone pairs
S
O O
O

20. Example 2: Lewis Diagram of SO3
5. Turn lone pairs into double or triple bonds tp give every
atom an octet (or duet).
S
O O
O